The invention described herein may be manufactured, licensed, and used by or for the U.S. Government.
1. Field of the Invention
The present invention relates to devices and methods for aerosol dispersion. More particularly, the claimed devices and methods use propellant gas generation. Most particularly, the devices and methods provide a non-explosive means for propellant disseminated aerosol payloads for military and civilian purposes.
2. Brief Description of the Related Art
Aerosols are the suspension of solid or liquid particles in the atmosphere. Aerosols are used in the military to defensively position and protect combat forces. During operations, a military force may be targeted visually or by means of ultraviolet, infrared (IR) or millimeter (MM) wave radar sensors. To counter this targeting, various types of filler payloads are used for aerosol dissemination, thereby obscuring and protecting the potential targets. These payloads include smokes to prevent visual detection, brass flakes that interfere with IR tracking and carbon fiber payloads to block energy in the MM region of the electromagnetic spectrum.
The military uses high explosive (HE) devices or grenades to disperse a variety of particle payloads into the atmosphere. HE devices and grenades, however, create a fragmentation hazard. In addition, both employ time delays, i.e., there is a delay from the time the grenade is fired until it explodes and creates an aerosol cloud. The military also uses pneumatic means, such as bleed air from a turbine engine, to disseminate aerosols. However, these aerosol systems are dependent on the vehicle as a source of dissemination air.
In addition, the prior art of military smoke pots can only screen in the visible and near infrared regions of the electromagnetic spectrum because the prior art relies on chemical decomposition of the filler to generate the gases that force the obscurant (a product of the decomposition reaction) into the atmosphere. The reliance on decomposition of the aerosol filler limits the prior art to the visible and near infrared spectrum because fillers that screen the far infrared and millimeter spectrum do not undergo such decomposition reactions. Attempts have been made to mix such fillers with those that decompose, but the results have been poor, i.e., the fillers that do not decompose are melted, destroyed or otherwise not lofted into the atmosphere.
Aerosols are also used in the civilian world for police and firefighting purposes. Police disperse riot control aerosols into crowds and as personal protectants and incapacitating agents. Firefighters use aerosols to remove fire sustaining elements, such as heat and oxygen. Currently, aerosols used by police and firefighters are provided by either spray containers, or grenades, that generally require an initiation time delay or by remote hoses or vehicles.
In view of the foregoing, improvements in the dispersal of aerosols are needed. The present invention addresses these needs by providing devices and methods for rapid aerosol dissemination. The present invention operates according to many of the principles disclosed in U.S. Pat. No. 6,047,644, which was issued to Applicant on Apr. 11, 2000, and which discloses an aerosol-filled cartridge that uses gases from ignited propellant to disperse the aerosol fill directly into the atmosphere. The present invention, however, includes elements, features and methods not disclosed or claimed in the ""644 patent.
The present invention includes a device comprising at least one cartridge formed by a casing having a base end and a retainer end; a firing initiator mounted in the base end and extending to a propellant near the base end of the casing; a diffuser inside the casing and on a side of the propellant opposite the base end; a clearing pad adjacent to the diffuser on a side of the diffuser opposite the base end; a filler area inside the casing and adjacent to the clearing pad on a side of the clearing pad opposite the base end, the filler area containing filler capable of forming an aerosol; and a frangible end seal in the retainer end of the casing. Preferably, the propellant""s rate of reaction is slower than that of an explosive that generates a shock wave traveling at 2000 meters per second. More preferably, the propellant is a double-base propellant. A double-base propellant contains two active ingredients, generally nitrocellulose and nitroglycerine.
A preferred embodiment of the present invention is based on an M2A1 ammunition-type carrying case and includes a housing containing multiple cylindrical or substantially cylindrical versions of the above-described cartridges; an electric firing initiator controlled by an electronic control unit; a paper, wax or cloth membrane inside of each casing and adjacent to each diffuser on a side opposite the propellant; a clearing pad inside of each casing and adjacent to the diffuser or membrane on a side opposite the propellant; and wherein the filler is a powder having interstitial void space between the particles.
In a preferred embodiment, the invention comprises a single man-portable unit that provides sequenced dissemination of multiple aerosol plumes and the use of propellant gas generation in the instantaneous formation of those plumes. Such a device can be ground-employed like standard military smoke pots and used to release aerosols in a planned manner to screen military objectives.
Unlike prior art military smoke pots, which rely on decomposition of the filler itself as opposed to decomposition of a separate propellant, this invention can screen not only the visible region but also the infrared and the millimeter regions, depending on the type of filler. A titanium dioxide TiO2 fill can be used to screen in the visible region, graphite or brass flake can be used to screen in the infrared region and carbon fiber can be used to screen in the millimeter region. A combination of fill materials can be tailored so that more than one region can be screened simultaneously. The device can also be mounted on armored and wheeled vehicles for generating a continuous sequence of plumes for increasing vehicle self-protection from detection and hit acquisition from threat munitions.
The invention also encompasses various methods. One preferred method of use involves daisy chaining a plurality of the devices together in a master-slave network to achieve long and continuous aerosol clouds. Another preferred method of use is as a vehicle self-protection screening device. Another is as a crowd control device.
Also disclosed is a method for disseminating an aerosol by igniting a propellant within at least one solid container having a frangible end and containing filler capable of forming an aerosol. Preferably, the filler does not chemically decompose within the container, the propellant burns in an area of the container separate from the filler and the reaction rate of the propellant is less than that of an explosive that generates a shock wave traveling at 2000 meters per second. It is also preferable that the propellant be a double-base propellant, that the propellant and the filler be separated by a diffuser and that a clearing pad adjacent to the diffuser on a side opposite the propellant help sweep the filler out of the container after the propellant has been ignited. The igniting may be initiated by an electrical signal.